1. Field of the Invention
The present invention relates to a steering device in which when adjustment is performed in a telescopic adjustment mechanism, the release of fastening of an inner column by an outer column can be smoothly performed, whereby effective telescopic adjustment can be realized.
2. Description of the Related Art
A large number of steering devices equipped with a tilt-telescopic mechanism have been used. In particular, in manually operated devices, the outer column clamps the outer peripheral surface of the inner column from both sides in a substantially diametric direction, the clamping pressure is increased by a fastener constituted by a bolt shaft and an operation lever, and the inner column is strongly fixed to the outer column. Where the fastener is loosened, the clamping pressure is decreased, while the portion of the outer column that clamps the inner column is opened, the inner column can easily move in the axial direction with respect to the outer column, and telescopic adjustment can be performed.
Such a telescopic adjustment mechanism is disclosed in Japanese Patent Application Publication No. 2008-162422. Thus, Japanese Patent Application Publication No. 2008-162422 discloses a structure in which a spring member SPG in the form of a coil spring or a plate spring is disposed inside the slit 2b of the column 2 (see FIG. 7 of Japanese Patent Application Publication No. 2008-162422). Further, the steering column mechanism of Japanese Patent Application Publication No. 2008-162422 has a structure in which the energy is absorbed in a secondary collision by the relative movement of the inner column 1 and outer column 2 in the axial direction.
Where the operation lever 13 is rotated in a predetermined direction, the opposing cam surfaces of the cam mechanism 12 are stuck, thereby generating an axial force acting on the clamp bolt 18 and shifting a pair of tilt brackets 3 toward each other (see FIG. 2 in Japanese Patent Application Publication No. 2008-162422). Where a pair of tilt brackets 3 is shifted toward each other, the slit 2b of the outer column 2 is impelled in the closing direction. Therefore, the inner diameter of the outer column 2 decreases and therefore a pressure is applied to the outer periphery of the inner column 1 and an adequate friction force is generated.
Since the spring member SPG is disposed inside the slit 2b of the outer column 2, part of the slit 2b is impelled in the opening direction, the fastening force of the outer column 2 is changed, regardless of the axial force of the clamp bolt 18, and the friction force on the contact surface of the inner column 1 and the outer column 2 is adjusted. As a result, the amount of energy absorbed in a secondary collision is adjusted.